This invention relates to an imaging device, such as a copying apparatus, utilizing a photosensitive recording sheet.
Prior art imaging device includes a type utilizing a photo sensitive recording sheet which comprises a paper sheet and microcapsules supported on said paper sheet and enveloping therein a dye precursor and a photo-curable resin. One example of said photosensitive recording sheets has been disclosed in the U.S. Pat. No. 4,399,209 or 4,440,846. The microcapsules are cured to become a rigid body when the surface of the recording sheet of this type is exposed to light, whereas the microcapsules not subjected to light exposure are not cured and therefore easily collapsible by applying pressure thereto.
Utilizing such characteristics, it has recently been proposed to form a latent image on the recording sheet by exposing the sheet surface in response to given image information, then destroy the uncured microcapsules by applying pressure to the sheet surface to allow the inside dye precursor to flow out, whereby the dye precursor reacts with a color developing agent precoated on the recording sheet itself or another transfer sheet to thereby form thereon a visible image, as disclosed in the U.S. Ser. No. 33,331. With this imaging device, it is possible to provide a desired duplicated image with high resolution and clearness and the maintenance thereof becomes easier because no toner powder is used.
In this prior art imaging device the recording sheet is prepared as a continuous paper wound into a roll and a takeup roller is employed for winding up a free end of the rolled paper, to thereby meet the requirement that the recording sheet supporting thereon collapsible microcapsules be travelled through the device between the light exposure section and the developing section, while applying no pressure to the sheet surface.
The rolled paper system adopted in this prior art imaging device is, as above described, preferred from a standpoint of contact-free conveyance of the recording sheet inside the apparatus. However, this system makes it difficult to separate the recording sheet from the transfer sheet after they come into contact under pressure at the developing station, that is, the transfer sheet would tend to be wound by the roller together with the recording sheet.
Another disadvantage encountered with actual use of such a prior art imaging device is that the recording sheet may often be exposed to ambient light during its travel from a supply source to the developing station, which makes it impossible to duplicate a photo-image exactly corresponding to the given image information. This becomes a fatal shortcoming especially when the rolled paper system is adopted, because the rolled paper is stored in the device for a long period of time so that the microcapsules contained in the rolled paper would tend to be hardened with time.
In the light exposure process, the light is projected onto the surface of the recording sheet mounted on an exposure platform, a portion of which is transmitted through the recording sheet and then reflected from the exposure platform, resulting in that the recording sheet is again exposed to the reflected light. Thus, the image profile once formed by the original projecting light would be blurred or deformed by the reflection to reduce resolution.